The present invention generally relates to a liquid crystal switching apparatus and, in particular, relates to one such apparatus including a plurality of juxtaposed liquid crystal switching devices.
The demand for optical switches has become readily apparent to the optical industry in recent years due to the rapid and continued expansion of the use of optical fibers for carrying information. One major field that is inexorably moving to the use of optical fibers is telecommunications. Most applications in telecommunications require the use of a substantial number of optical switches. Hence, it becomes highly desirable to reduce not only the cost of each switch, but also to reduce the cost and complexity for developing a switching matrix that is capable of interconnecting a plurality of subscribers both between themselves and with an external transmission medium.
Recently, optical switching devices utilizing liquid crystal material to selectively redirect the path of a light beam have been suggested.
In early versions of such optical switches, a liquid crystal material was sandwiched between a pair trapezoidal prisms. Various arrangements and configurations of this type of liquid crystal optical switches are described and discussed in U.S. Pat. No. 4,201,442 issued to McMahon et al. on May 6, 1980, U.S. Pat. No. 4,278,327 issued McMahon et. al. on July 14, 1981, and U.S. Pat. No. 4,385,799 issued to Soref on May 31, 1983. Each of the individual switch designs described in the above-referenced U.S. Patents requires at least one pair of matched trapezoidal prisms in addition to sophisticated optical collimators. The trapezoidal prisms, as well as the collimators, are quite expensive. Further, the assembly of such switches requires accurate alignment of the various parts thereof to ensure optical path accuracy. In addition to the expense of the materials and the necessary accuracy for the optical alignment, the devices generally exhibit considerable internal reflections unless the indexes of refraction of the prism materials, the electrodes, and the liquid crystal material are accurately matched.
More recently, liquid crystal switches and devices have been described and discussed in the following co-pending U.S. patent applications Ser. Nos.: 795,156; 795,151; 795,152; 795,150; 795,155; 795,138; 795,148; 795,157; 795,154; 795,149; 795,296 all filed on Nov. 11, 1985 and assigned to the assignee hereof.
One of the major advantages of the devices described in these applications is that they can be manufactured from rather inexpensive material by relatively conventional fabrication techniques, such as, plastic injection molding techniques.
However, the above discussed devices do not generally provide a unitary, or bulk, arrangement particularly adapted for configuring a switch matrix.
Consequently, in order to enhance both the applicability and to further realize the inherent advantages of liquid crystal switching devices, a liquid crystal switching apparatus having a plurality of liquid crystal switching devices that can be readily configured into a switching matrix is needed to maximize the usefulness of such devices within an optical fiber based signaling system.